This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 5 |
| 3 | 31 |
| 4 | 219 |
| 5 | 1672 |
| 6 | 13439 |
| 7 | 112043 |
| 8 | 960017 |
| 9 | 8402085 |
| 10 | 74791408 |
| 11 | 675033956 |
| 12 | 6163120105 |
| 13 | 56820187321 |
| 14 | 528231686315 |
| 15 | 4946304326883 |
| 16 | 46609889424547 |
| 17 | 441664236745594 |
| 18 | 4205848369345681 |
| 19 | 40228631544942031 |
| 20 | 386317524696654392 |
| 21 | 3723196299965400616 |